Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
LO(4)		       FreeBSD Kernel Interfaces Manual			 LO(4)

NAME
     lo	-- software loopback network interface

SYNOPSIS
     device loop

DESCRIPTION
     The loop interface	is a software loopback mechanism which may be used for
     performance analysis, software testing, and/or local communication.  As
     with other	network	interfaces, the	loopback interface must	have network
     addresses assigned	for each address family	with which it is to be used.
     These addresses may be set	or changed with	the SIOCSIFADDR	ioctl(2).  The
     loopback interface	should be the last interface configured, as protocols
     may use the order of configuration	as an indication of priority.  The
     loopback should never be configured first unless no hardware interfaces
     exist.

     If	the transmit checksum offload capability flag is enabled on a loopback
     interface,	checksums will not be generated	by IP, UDP, or TCP for packets
     sent on the interface.

     If	the receive checksum offload capability	flag is	enabled	on a loopback
     interface,	checksums will not be validated	by IP, UDP, or TCP for packets
     received on the interface.

     By	default, both receive and transmit checksum flags will be enabled, in
     order to avoid the	overhead of checksumming for local communication where
     data corruption is	unlikely.  If transmit checksum	generation is dis-
     abled, then validation should also	be disabled in order to	avoid packets
     being dropped due to invalid checksums.

DIAGNOSTICS
     lo%d: can't handle	af%d.  The interface was handed	a message with
     addresses formatted in an unsuitable address family; the packet was
     dropped.

SEE ALSO
     inet(4), intro(4)

HISTORY
     The lo device appeared in 4.2BSD.	The current checksum generation	and
     validation	avoidance policy appeared in FreeBSD 8.0.

FreeBSD	9.3			March 15, 2009			   FreeBSD 9.3

NAME | SYNOPSIS | DESCRIPTION | DIAGNOSTICS | SEE ALSO | HISTORY

Want to link to this manual page? Use this URL:
<http://www.freebsd.org/cgi/man.cgi?query=lo&manpath=FreeBSD+9.3-RELEASE>

home | help